pull·back /ˈpʊlˌbæk/
  拉回,障礙,阻擾
  Pull·back n.
  1. That which holds back, or causes to recede; a drawback; a hindrance.
  2. Arch The iron hook fixed to a casement to pull it shut, or to hold it party open at a fixed point.
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  pullback
       n 1: a device (as a decorative loop of cord or fabric) for
            holding or drawing something back; "the draperies were
            drawn to the sides by pullbacks" [syn: tieback]
       2: (military) the act of pulling back (especially an orderly
          withdrawal of troops); "the pullback is expected to be
          over 25,000 troops"